Performance heat exchanger, in particular an evaporator

ABSTRACT

A heat exchanger for exchange of heat between a first fluid and a second fluid comprises a stack of pockets ( 1 ) mutually aligned in a longitudinal direction and having two header boxes ( 16, 17 ) that are mutually juxtaposed in a lateral direction. The first fluid is injected into an upstream connecting channel ( 12 ) by a longitudinal nozzle ( 22 ) passing through a heat exchanger end face ( 5 ) remote from the upstream connecting channel, and at least one other connecting channel ( 14 ). This longitudinal nozzle has a cross section of oblong general shape, whose greatest dimension is parallel to the greatest dimension of the pockets. The heat exchanger may be produced particularly in the form of an evaporator for an air-conditioning device for the passenger compartment of a vehicle.

BACKGROUND OF THE INVENTION

The invention relates to heat exchangers, especially for motor vehicles.

It relates more particularly to a heat exchanger for heat exchangebetween a first fluid and a second fluid, comprising a stack of pocketsmutually aligned in a longitudinal direction and having two header boxesthat are mutually juxtaposed in a lateral direction and are each formedby the alignment, in the longitudinal direction, of inlet or outletchambers belonging respectively to the different pockets, the headerboxes as a whole being divided into at least three connecting channels,and in which exchanger the first fluid is injected into an upstreamconnecting channel by a longitudinal nozzle passing through a heatexchanger end face remote from the upstream connecting channel, and atleast one other connecting channel formed by other pockets.

DESCRIPTION OF THE PRIOR ART

The prior art, particularly in EP 0 911 595, already discloses a heatexchanger of this type, in which the connecting channels that belong toone header box all come one after the other in the longitudinaldirection and do not communicate directly with each other, whereaswithin each connecting channel the inlet or outlet chambers communicatewith each other via openings in the walls of the pockets.

The pockets define a pathway for the first fluid between an upstreamconnecting channel adjacent to a first longitudinal end of the stack anda downstream connecting channel adjacent to the second longitudinal endof the stack, passing back and forth between a connecting channelbelonging to one of the header boxes and a connecting channel belongingto the other header box, via U paths, each of which connects togetherthe inlet chamber and outlet chamber of one pocket. The upstream anddownstream connecting channels are connected to inlet and outletpassages provided at one of said longitudinal ends, one directly and theother through the aforementioned longitudinal nozzle. This nozzle runsthrough the openings of the connecting channels interposed between thisend and said other connecting channel.

Such heat exchangers are in wide use as evaporators in air-conditioningdevices for the passenger compartment of vehicles.

The pockets are each made up of two metal sheets pressed into the formof troughs in which the concavities are turned toward each other andwhich are connected together in a fluidtight manner around theirperiphery, the inlet and outlet chambers being defined by regions of thetroughs that are deeper than the remaining regions, so that a gap isleft between two neighboring pockets, between said remaining regions,for the passage of the second fluid in the lateral direction, and saidopenings are formed in the bottoms of the troughs which are in mutualfluidtight contact around the openings.

The two troughs of each pocket are also connected fluidtightly in amiddle area halfway across their widths and along a notable fraction oftheir length beginning at a first end edge, the two branches of the saidU path extending on either side of said middle area, as do said deeperregions of the troughs, situated near said first end edge.

In the known heat exchangers of this type, the longitudinal nozzle, alsoknown as a pipette, has a circular cross section as taught by thepublication EP 0 911 595.

One of the objects of the invention is to further improve the operatingcharacteristics of these exchangers.

It is also designed to improve the passage of the first fluid and thebalance of the heat exchanger.

SUMMARY OF THE INVENTION

To this end the invention provides a heat exchanger of the type definedin the introduction, in which the longitudinal nozzle has a crosssection of oblong general shape, whose greatest dimension is parallel tothe greatest dimension of the pockets.

It has been found that, due to its oblong cross section, thislongitudinal nozzle improves the passage of the first fluid and can alsobe positioned in such a way as not to partly block the chambers definedin the pockets. Furthermore, with this special shape, the longitudinalnozzle is more suitable for the shape of the header boxes in the case inwhich the plates are narrow (in the lateral direction), typically lessthan 60 mm wide.

Optional features of the invention, whether supplementary oralternative, are set out below:

-   -   The cross section of the longitudinal nozzle is of oval general        shape.    -   The longitudinal nozzle is fixed to an end box fitted to said        end face.    -   The end box has a first cavity with an opening into which the        longitudinal nozzle passes and a second cavity with an opening        leading into a downstream connecting channel adjacent to said        end of the heat exchanger.    -   The end box accommodates a shaped plate defining an entrance        piece communicating with the first cavity and an exit piece        communicating with the second cavity.    -   The longitudinal nozzle is crimped to the edges of the opening        of the first cavity.    -   The longitudinal nozzle is brazed to the edges of an opening        allowing communication between the upstream connecting channel        and an adjacent connecting channel through which the        longitudinal nozzle passes.    -   The adjacent connecting channel extends to the end face of the        heat exchanger.    -   The longitudinal nozzle is brazed to the outer edge of the        openings that allow communication between adjacent pockets.    -   The longitudinal and lateral directions are essentially        horizontal and the header boxes are located at the top of the        exchanger.

DESCRIPTION OF THE DRAWINGS

The description that follows, offered purely by way of example, refersto the appended drawings, in which:

FIG. 1 is a partial view of a heat exchanger according to the invention,in section on the line marked I—I in FIG. 2;

FIG. 2 is a top view of the heat exchanger, in section on the linemarked II—II in FIG. 1;

FIG. 3 is a view in transverse section through the longitudinal nozzleof the heat exchanger of FIGS. 1 and 2;

FIG. 4 is a detail on an enlarged scale from FIG. 2; and

FIG. 5 is a perspective view showing a longitudinal nozzle/end boxassembly suitable to form part of the heat exchanger of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The heat exchanger shown in the drawings is an evaporator intended foran air-conditioning device for the passenger compartment of a motorvehicle. It comprises a multiplicity of pockets 1 stacked together in anessentially horizontal longitudinal direction and each made up of twometal sheets pressed into trough shapes 2 and 3. The latter areidentical with each other and have their concavities turned toward eachother, i.e. toward second and first longitudinal ends 5, 4 of the stack.Each trough has an outer edge 6 situated in a vertical plane, and theouter edges 6 of the two troughs forming one pocket are assembledfluidtightly together by brazing, to define the internal volume of thepocket.

Each trough also has at its top, two regions 7 that are deeper than theremaining region 8, this latter region occupying the greater part of theheight of the trough, below the regions 7 (FIG. 2). These two deeperregions of each trough, which are juxtaposed from left to right in thefigures, define in each pocket an inlet chamber and an outlet chamberfor a first fluid, which in the present case is the coolant.

The inlet chamber and outlet chamber of each pocket are separated fromeach other by a fluidtight joining area 9 between the two troughs,halfway across the width of the pocket, this joining area meeting theedge 6 at the top end 10 of the pocket and continuing downward, stoppingjust short of the lower end of the pocket, in such a way as to define inthe pocket, opposite the regions 8 of the troughs, a U path for thefluid between the inlet chamber and the outlet chamber (FIG. 2).

The bottom of each trough is interrupted, in each of the deeper regions7, by an opening 11, and where the bottoms of one trough 2 are turnedtoward the bottoms of an adjacent trough 3, the bottoms are bondedfluidtightly together around the openings, by brazing.

The alignment of inlet/outlet chambers on the left-hand side of thefigures forms a header box 16, and the alignment of inlet/outletchambers on the right-hand side forms a header box 17 (FIG. 1). Theheader box 16 is subdivided by a transverse partition 18 into aconnecting channel 12, extending from this partition to the end 4 of thestack, and a connecting channel 14 extending from the partition to theend 5. Similarly, a transverse partition 19, further from the end 4 thanthe partition 18, separates the header box 17 into a connecting channel13 adjacent to the end 4 and a connecting channel 15 adjacent to the end5. An end plate 20 is brazed to the bottom of the trough 3 situated atthe end 4 of the stack, while an end box 21 (see also FIGS. 4 and 5) isbrazed to the bottom of the trough 3 situated at the end 5 of the stack.In this way, the openings 11 of the troughs are closed off, which helpsto define the connecting channels. The inlet/outlet chambers forming oneconnecting channel communicate with each other via the openings 11 inthe troughs 2, 3.

A longitudinal nozzle 22, also known as a “pipette”, extends the fulllength of the connecting channel 14. It is connected fluidtightly to theend box 21 and passes fluidtightly through the intermediate partition18, in such a way as to allow communication between the connectingchannel 12 (the upstream connecting channel) and that part of thecoolant circuit which is situated upstream of the evaporator.

Also, the end box 21 comprises an opening 23 leading into the connectingchannel 15, placing the latter in communication with the downstream partof the circuit.

The coolant enters the connecting channel 12 via the longitudinal nozzle22 before passing into the connecting channel 13 by following theparallel U paths of a first group of pockets. It is then transferred tothe connecting channel 14 via the U paths of a second group of pockets,and thence to the connecting channel 14 via the U paths of a third andfinal group of pockets. The fluid finally leaves the evaporator throughthe outlet opening 23. As it travels around the U paths, the fluidreceives heat from an air stream passing horizontally through theevaporator from right to left as indicated by the arrow F1, via the gapsseparating the opposing pockets of the regions 8 of the troughs.

In accordance with the invention, the nozzle 22 has an oblong crosssection, of oval form in the example (FIG. 3), the greatest dimension ofwhich is parallel to the greatest dimension of the pockets. This meansthat the greatest dimension of the oval section is vertical when viewingFIG. 1.

Also, the nozzle 22 is offset from the center of the openings 11 of thetroughs defining the header box 16. In the example shown, the nozzle isoffset toward the exterior, in this case to the left, that is downstreamin terms of the air stream F1. More particularly, the outline of eachopening 11 is of an oval shape and is made up of two horizontal straightline segments 30 and two arcs of a circle 31 whose concavities aretoward each other and which are joined to the segments 30 (FIG. 1). Thenozzle 22 is in contact with one of the two arcs of a circle 31 (the oneon the left) on the edge of the openings through which it passes, and isbrazed to this edge all the way around the length of the leftmost arc ofa circle 31. Consequently, the greatest dimension of the cross sectionof the nozzle 22 is perpendicular to the greatest dimension of theopening 11 (FIG. 1).

As FIGS. 4 and 5 show, the longitudinal nozzle 22 is fixed to the endbox 21 which is fitted to the end face 5 of the evaporator. This end box21 has a first cavity 32 with an oval opening 33 through which thelongitudinal nozzle 22 enters. The longitudinal nozzle 22 is crimped tothe edges of this opening 33. The end box 21 also has a second cavity 34in which the abovementioned opening 23 is formed and which connects withthe downstream connecting channel 15. The end box 21 in this case has atwo-trough shape similar to that of a plate 2.

This end box 21 accommodates a shaped plate 35 (FIGS. 2 and 4) thatdefines an entrance piece 36 communicating with the cavity 32 andtherefore with the nozzle 22 and an exit piece 37 communicating with thesecond cavity 34, and therefore with the outlet opening 23. In this wayan entrance piece and an exit piece are formed on the end of theevaporator, that is at the end of the stack of plates.

The longitudinal nozzle can be brazed to the edges of an opening 11allowing communication between the upstream connecting channel 12 and anadjacent connecting channel 14 traversed by this longitudinal nozzle.This adjacent connecting channel 14 extends to the end face 5 of theheat exchanger.

In addition, the longitudinal nozzle 22 is brazed to the outer edge ofthe openings 11 that provide communication between each pocket and itsneighbor.

In the embodiment illustrated, the longitudinal and lateral directionsof the exchanger are essentially horizontal, while the header boxes 16and 17 are situated at the top of the exchanger (FIG. 1).

It has been observed that due to the oblong shaping of the cross sectionof the longitudinal nozzle, the performance of the heat exchanger, inthis case of the evaporator, is improved.

More specifically, it improves the passage of the fluid by limiting theinternal head loss and enhancing its performance.

Due to its oblong shape, the longitudinal nozzle can be positioned sothat it does not partly block the channels, and it is more suitable forthe shape of the boxes.

The nozzle can thus be accommodated in plates of a relatively narrowwidth, typically less than 60 mm. This also improves the balance of theevaporator.

A significant improvement in the performance of the evaporator of theinvention is observed.

The arrangement according to the invention also improves the uniformityof the exchange of heat through the volume of the evaporator, andconsequently the uniformity of temperature distribution in the airstream coming out of the evaporator, with attenuation of the phenomenaof hot and cold spots.

Moreover, the brazing of the longitudinal nozzle around a considerablelength of the edges of the openings improves stiffness and reducesoperational noise.

In the invention, the cross section of the nozzle may have an oblongshape that differs from an oval shape, for example an elliptical orrectangular or other shape.

The invention has a particular application to the construction ofevaporators for vehicle air-conditioning devices.

1. A heat exchanger for heat exchange between a first fluid and a secondfluid, particularly an evaporator for an air-conditioning device for thepassenger compartment of a motor vehicle, comprising a stack of pockets(1) mutually aligned in a longitudinal direction and having two headerboxes (16, 17) that are mutually juxtaposed in a lateral direction andare each formed by the alignment, in the longitudinal direction, ofinlet or outlet chambers belonging respectively to the differentpockets, the header boxes as a whole being divided into at least threeconnecting channels, in which exchanger the first fluid is injected intoan upstream connecting channel (12) by a longitudinal nozzle (22)passing through a heat exchanger end face (5) remote from the upstreamconnecting channel, and at least one other connecting channel (14)formed by other pockets, in which exchanger said longitudinal nozzle(22) has a cross section of oblong general shape, whose greatestdimension is parallel to the greatest dimension of the pockets (1). 2.The heat exchanger as claimed in claim 1, in which the cross section ofthe longitudinal nozzle (22) is of oval general shape.
 3. The heatexchanger as claimed in claim 1, in which the longitudinal nozzle (22)is fixed to an end box (21) fitted to said end face (5).
 4. The heatexchanger as claimed in claim 3, in which the end box (21) has a firstcavity (32) with an opening (33) into which the longitudinal nozzle (22)passes and a second cavity (34) with an opening (23) leading into adownstream connecting channel (15) adjacent to said end (5) of the heatexchanger.
 5. The heat exchanger as claimed in claim 4, in which the endbox (21) accommodates a shaped plate (35) defining an entrance piece(36) communicating with the first cavity (32) and an exit piece (37)communicating with the second cavity (34).
 6. The heat exchanger asclaimed in claim 4, in which the longitudinal nozzle (22) is crimped tothe edges of the opening (33) of the first cavity (32).
 7. The heatexchanger as claimed in claim 1, in which the longitudinal nozzle (22)is brazed to the edges of an opening (11) allowing communication betweenthe upstream connecting channel (12) and an adjacent connecting channel(14) through which the longitudinal nozzle (22) passes.
 8. The heatexchanger as claimed in claim 7, in which said adjacent connectingchannel (22) extends to the end face (5) of the heat exchanger.
 9. Theheat exchanger as claimed in claim 1, in which the longitudinal nozzle(22) is brazed to the outer edge of the openings (11) that allowcommunication between adjacent pockets (1).
 10. The heat exchanger asclaimed in claim 1, in which the longitudinal and lateral directions areessentially horizontal and the header boxes (16, 17) are located at thetop of the exchanger.